Unfused thermal support area in 3D fabrication systems

ABSTRACT

According to examples, a three-dimensional (3D) fabrication system may include a controller that may control an agent delivery system to deposit a fusing agent onto a fusing area of a layer of particles of build material. The controller may also control the agent delivery system to deposit an energy absorbing agent onto an unfused thermal support area of the layer of particles, the unfused thermal support area being located adjacent to the fusing area. The controller may further control an energy supply system to supply energy, in which supply of the energy is to cause the particles on which the fusing agent has been deposited to melt and a temperature of the particles in the unfused thermal support area to be raised to a level that is below a melting point temperature of the particles.

BACKGROUND

In three-dimensional (3D) printing, an additive printing process isoften used to make three-dimensional solid parts from a digital model.Some 3D printing techniques are considered additive processes becausethey involve the application of successive layers or volumes of a buildmaterial, such as a powder or powder-like build material, to an existingsurface (or previous layer). 3D printing often includes solidificationof the build material, which for some materials may be accomplishedthrough use of heat and/or a chemical binder.

BRIEF DESCRIPTION OF THE DRAWINGS

Features of the present disclosure are illustrated by way of example andnot limited in the following figure(s), in which like numerals indicatelike elements, in which:

FIG. 1A shows a diagram of an example 3D fabrication system that mayform an example unfused thermal support area to reduce a rate at whichparticles forming a portion of a 3D object thermally bleeds;

FIG. 1B shows an isometric view of a layer of particles on which afusing area and an example unfused thermal support area have beenformed;

FIGS. 1C-1E, respectively, show cross-sectional side views of layers ofparticles on which a fusing area and an example unfused thermal supportarea have been formed;

FIG. 2 shows a diagram of another example 3D fabrication system that mayform an unfused thermal support area to reduce a rate at which particlesforming a portion of a 3D object thermally bleeds;

FIG. 3 shows a block diagram of an example apparatus that may cause anunfused thermal support area to be formed adjacent to a selected areaduring formation of a portion of a 3D object; and

FIG. 4 shows a flow diagram of an example method for forming an unfusedthermal support area.

DETAILED DESCRIPTION

Disclosed herein are 3D fabrication systems, apparatuses, and methodsthat may be implemented to deposit a fusing agent onto a fusing area ofa layer of particles of build material and to deposit an energyabsorbing agent to form an unfused thermal support area adjacent to thefusing area. In addition, the 3D fabrication systems and apparatusesdisclosed herein may be implemented to supply energy onto the particles,such that the fusing agent deposited on the particles absorbs the energyand causes the temperature of those particles to rise to a level above amelting point temperature of the particles. The particles in the fusingarea may thus melt and subsequently fuse together as the meltedparticles cool and solidify. In addition, the particles on which thefusing agent has not been deposited may not absorb sufficient energy toreach the melting point temperature.

However, the energy absorbing agent may be deposited in the unfusedthermal support area at a sufficiently low contone level to cause thetemperature of the particles in the unfused thermal support area toincrease without reaching the melting point temperature. The energyabsorbing agent may, in other examples, be deposited at a relativelyhigher contone level, but with a cooling agent or a defusing agent tokeep the temperature of the particles in the unfused thermal supportarea below the melting point temperature. In one regard, throughapplication of energy onto the energy absorbing agent, the temperatureof the particles in the unfused thermal support area may rise withoutreaching a level that causes those particles to melt and subsequentlyfuse together. In another regard, because the particles in the unfusedthermal support area may not fuse together, those particles may also notfuse with the particles in the fusing area. The particles in the unfusedthermal support area may thus increase a temperature around the unfusedthermal support area, including the fusing area.

As the particles in the fusing area may be at a higher temperature thanthe particles outside of the fusing agent, thermal bleed may occur fromthe particles in the fusing area to the particles outside of the fusingarea. That is, heat from the particles in the fusing area may betransferred to the particles in the areas surrounding the fusing area.When the fusing area is at or above a certain size, the particles in thefusing area may be heated and may remain heated at a sufficiently hightemperature such that the thermal bleed that occurs may be insufficientto prevent the particles from melting and fusing together as intended,e.g., to have an intended strength, rigidity, hardness, color,translucency, surface roughness, combinations thereof, or the like.However, when the size of the fusing area is below the certain size, therate at which thermal bleed occurs may result in the particles in thefusing area from failing to reach and/or remain at or above the meltingpoint temperature for sufficient melting to occur such that theparticles fuse together as intended. The certain size may pertain to athickness, a width, a length, an area, a volume, or combinationsthereof, of the fusing area, which may extend across multiple layers ofparticles.

According to examples, by forming the unfused thermal support areaadjacent to the fusing area, the rate of thermal bleed from theparticles in the fusing area may be reduced. In this regard, the unfusedthermal support area may facilitate the melting and fusing together ofthe particles in the fusing area. In other words, because the particlesin the unfused thermal support area are at a higher temperature than theparticles outside of the unfused thermal support area and the fusingarea, a thermal gradient between the particles in the fusing area andthe particles in the unfused thermal support area may be smaller than athermal gradient between the particles in the fusing area and theparticles outside of the unfused thermal support area. As such, the rateat which heat is transferred from the particles in the fusing area tothe particles in the unfused thermal support area may be lower than therate at which heat is transferred from the particles in the fusing areato the particles outside of the unfused thermal support area.

As discussed herein, the unfused thermal support area may includeunfused particles and thus, the unfused thermal support area mayfacilitate the melting and fusing of the particles in the fusing area,particularly, when the fusing area is relatively small. According toexamples, the energy absorbing agent may be a degradable fluid that maydegrade within a certain period of time following receipt of the energyor in the presence of another agent. In these examples, the particlesupon which the energy absorbing agent has been deposited may berecycled.

Through implementation of the 3D fabrication systems, apparatuses, andmethods disclosed herein, 3D objects and/or sections of 3D objectshaving relatively small sizes, e.g., fine features, may be fabricated tohave substantially increased mechanical strength, more accurate colors,improved surface quality, more accurate translucency, or the like. Inaddition, these results may be achieved without fusing particles outsideof the particles that form the 3D objects, which may reduce overallcosts associated with fabricating objects with build material particlesas those particles may be reused.

Before continuing, it is noted that as used herein, the terms “includes”and “including” mean, but is not limited to, “includes” or “including”and “includes at least” or “including at least.” The term “based on”means “based on” and “based at least in part on.”

With reference first to FIG. 1A, there is shown a diagram of an example3D fabrication system 100 that may form an unfused thermal support areato reduce a rate at which particles forming a portion of a 3D objectthermally bleeds. It should be understood that the 3D fabrication system100 depicted in FIG. 1A may include additional components and that someof the components described herein may be removed and/or modifiedwithout departing from a scope of the 3D fabrication system 100disclosed herein.

The 3D fabrication system 100 may also be termed a 3D printer, a 3Dfabricator, or the like. Generally speaking, the 3D fabrication system100 may be implemented to fabricate 3D objects from particles 102 ofbuild material, which may also be termed build material particles 102.The particles 102 of build material may include any suitable materialincluding, but not limited to, a polymer, a plastic, a ceramic, a nylon,a metal, combinations thereof, or the like, and may be in the form of apowder or a powder-like material. Additionally, the particles 102 may beformed to have dimensions, e.g., widths, diameters, or the like, thatare generally between about 5 μm and about 100 μm. In other examples,the particles 102 may have dimensions that are generally between about30 μm and about 60 μm. The particles 102 may have any of multipleshapes, for instance, as a result of larger particles being ground intosmaller particles. In some examples, the powder may be formed from, ormay include, short fibers that may, for example, have been cut intoshort lengths from long strands or threads of material. The particles102 have been shown as being partially transparent to enable a fusingarea 104 and a thermal support area 106 to be visible. It should thus beunderstood that the particles 102 may not be transparent, but instead,may be opaque.

As shown in FIG. 1A, the 3D fabrication system 100 may include acontroller 110, an agent delivery system 120, and an energy supplysystem 130. The controller 110 may control the agent delivery system 120to deposit a fusing agent, which is represented by the arrow 122, onto afusing area 104 of a layer of particles 102. The controller 110 may alsocontrol the agent delivery system 120 to deposit an energy absorbingagent, which is represented by the arrow 124, onto an unfused thermalsupport area 106. The unfused thermal support area 106 may be formedadjacent to the fusing area 104 and may not form part of a 3D object tobe fabricated. The controller 110 may further control the energy supplysystem 130 to supply energy, which is represented by the arrow 132, ontothe layer of particles 102, the fusing area 104, and the unfused thermalsupport area 106.

The fusing agent 122 may be a liquid, such as an ink, a pigment, a dye,or the like, that may enhance absorption of energy 132 emitted from theenergy supply system 130. The agent delivery system 120 may deliver thefusing agent 122 in the form of droplets onto the layer of particles 102such that the droplets of fusing agent 122 may be dispersed on theparticles 102 and within interstitial spaces between the particles 102in the fusing area 104. In the fusing area 104, the droplets of fusingagent 122 may be supplied at a sufficient density, e.g., contone level,to enhance absorption of sufficient energy 132 to cause the temperatureof the particles 102 on which the fusing agent 122 has been deposited toincrease to a level that is above a melting point temperature of theparticles 102. In addition, the energy supply system 130 may supplyenergy 132 at a level that is insufficient to cause the particles 102upon which the fusing agent 122 has not been supplied to remain belowthe melting point temperature of the particles 102.

The energy absorbing agent 124 may also be a liquid, such as an ink, apigment, a dye, or the like, that may enhance absorption of energy 132emitted from the energy supply system 130. The agent delivery system 120may deliver the energy absorbing agent 124 in the form of droplets ontothe layer of particles 102 such that the droplets of energy absorbingagent 124 may be dispersed on the particles 102 and within interstitialspaces between the particles 102 in the unfused thermal support area106. In the unfused thermal support area 106, the droplets of energyabsorbing agent 124 may be supplied at a sufficiently low density, e.g.,contone level, to absorb sufficient energy 132 to cause the temperatureof the particles 102 on which the energy absorbing agent 124 has beendeposited to increase, but to a level that is below the melting pointtemperature of the particles 102. In other words, the droplets of energyabsorbing agent 124 may be supplied at a sufficiently low density toincrease the temperature of the particles 102 in the unfused thermalsupport area 106 without causing those particles 102 to fuse together.In addition or in other examples, a cooling agent and/or a defusingagent may be combined with the energy absorbing agent 124, such that thecombination of agents may increase the temperature of the particles 102upon which the combination has been deposited without causing thoseparticles 102 to fuse together.

According to examples, the energy absorbing agent 124 may be a sameagent as the fusing agent 122. In other examples, the energy absorbingagent 124 may be a different agent than the fusing agent 122. By way ofparticular example, the energy absorbing agent 124 may be a degradableagent that is to degrade within a predetermined time period followingreceipt of the supplied energy 132 or when placed into the presence ofanother agent. For instance, the degradable agent may be a liquid thatis to degrade, e.g., evaporate, disintegrate, or the like, for instance,after a few minutes, a few hours, etc., after receiving the energy 132.In some examples, the degradable agent may be degradable through receiptof a chemical agent, for instance, that degrades the degradable agentwithout degrading or harming the particles 102. The degradable agent maydegrade during fabrication of an object or following fabrication of theobject. In any of these examples, the particles 102 upon which theenergy absorbing agent 124 has been deposited may be reused, e.g.,recycled, following degradation of the energy absorbing agent 124. Inany of these examples, the density level, e.g., the contone level, atwhich the droplets of the energy absorbing agent 124 are deposited ontothe unfused thermal support area 106 may substantially be lower than thedensity level at which the droplets of the fusing agent 122 aredeposited onto the fusing area 104. In addition or in other examples,the energy absorbing agent 124 may be mixed with a cooling agent and/ora defusing agent.

As the particles 102 in the fusing area 104 may be at a highertemperature than the particles 102 on which the fusing agent 122 has notbe been deposited, thermal bleed may occur from the particles 102 in thefusing area 104 to the particles 102 outside of the fusing area 104.That is, heat from the particles 102 in the fusing area 104 may betransferred to the particles 102 in the areas surrounding the fusingarea 104. When the fusing area 104 is at or above a certain size, theparticles 102 in the fusing area 104 may be heated and may remain heatedat a sufficiently high temperature such that the thermal bleed thatoccurs may be insufficient to prevent the particles 102 from melting andfusing together as intended, e.g., to have an intended strength,rigidity, hardness, color, translucency, surface roughness, combinationsthereof, or the like. However, when the size of the fusing area 104 isbelow the certain size, the rate at which thermal bleed occurs mayresult in the particles 102 in the fusing area 104 from failing to reachand/or remain at or above the melting point temperature for sufficientmelting to occur such that the particles 102 fuse together as intended.The certain size may pertain to a thickness, a width, a length, an area,a volume, or combinations thereof, of the fusing area 104, which mayextend across multiple layers of particles 102. The certain size mayalso be referenced herein as a predefined size.

The certain size may depend, for instance, upon the type of particle102, the type of fusing agent 122, the type and/or strength of energy132 emitted by the energy supply system 130, combinations thereof, andthe like. In some examples, the certain size may be determined throughtesting of different combinations of particle 102 types, fusing agent122 types, energy 132 types and/or strengths, etc. In addition or inother examples, the certain size may be the same for differentcombinations of particle 102 types, fusing agent 122 types, energy 132types and/or strengths, etc. In any of these examples, the controller110 may form the unfused thermal support area 106 adjacent to the fusingarea 104 when the fusing area 104 is below the certain size and may notform the unfused thermal support area 106 when the fusing area 104 is ator above the certain size.

According to examples disclosed herein, the unfused thermal support area106 may reduce the rate at which thermal bleed occurs from the particles102 in the fusing area 104. In this regard, the unfused thermal supportarea 106 may facilitate the melting and fusing together of the particles102 in the fusing area 104. In other words, because the particles 102 inthe unfused thermal support area 106 are at a higher temperature thanthe particles 102 outside of the unfused thermal support area 106 andthe fusing area 104, a thermal gradient between the particles 102 in thefusing area 104 and the particles 102 in the unfused thermal supportarea 106 may be smaller than a thermal gradient between the particles102 in the fusing area 104 and the particles 102 outside of the unfusedthermal support area 106. As such, the rate at which heat is transferredfrom the particles 102 in the fusing area 104 to the particles 102 inthe unfused thermal support area 106 may be lower than the rate at whichheat is transferred from the particles 102 in the fusing area 104 to theparticles 102 outside of the unfused thermal support area 106. This mayresult in the particles 102 in the fusing area 104 to be at a highertemperature, which may reduce the effects of thermal bleed and theparticles 102 may thus reach and/or remain at a sufficiently hightemperature for the particles 102 to melt and fuse together as intended.

The unfused thermal support area 106 may have a similar shape to thefusing area 104 or may have a different shape from the fusing area 104.The unfused thermal support area 106 may extend at a same distance fromthe entire periphery of the fusing area 104 or may extend differentdistances at different locations around the fusing area 104. Thedistance or distances at which the unfused thermal support area 106extends from the fusing area 104, e.g., the width or widths of theunfused thermal support area 106, may be based on the amount oftemperature increase for the particles 102 in the fusing area 104 tofuse as intended. The width or widths at which the unfused thermalsupport area 106 may be determined based on testing, estimations ofthermal bleed, correlations between fusing area 104 sizes and thermalbleed, etc. In addition, in various examples, the unfused thermalsupport area 106 may be formed to increase a local temperature aroundthe unfused thermal support area 106 to, for instance, make thetemperature distribution on a particle bed more uniform.

According to examples, and as shown in FIG. 1A, the entire fusing area104 may be below the certain size. In these examples, the unfusedthermal support 106 may be formed around the entire periphery of thefusing area 104. In other examples, and as shown with respect to FIG.1B, the fusing area 104 may have an irregular shape. That is, the fusingarea 104 may include a first feature 140 that is below the certain sizeand a second feature 142 that is above the certain size. In theseexamples, a unfused thermal support area 106 may be formed adjacent tothe first feature 140 without a unfused thermal support area 106 beingformed adjacent to the second feature 142. In one regard, the unfusedthermal support area 106 may selectively be formed to increase thetemperature of the particles 102 in the areas of an object that arebelow the certain size. In addition, the unfused thermal support area106 may not be adjacent to the second feature 142, e.g., immediatelynext to second feature 142, as the second feature 142 may reach and/orremain at a temperature above the melting point temperature of theparticles 102 due to the sufficiently large size of the second feature142. As such, thermal bleed of the particles 102 forming the secondfeature 142 may not be sufficient to prevent the particles 102 formingthe second feature 142 from melting and fusing together as intended.

Turning now to FIGS. 1C-1E, there are respectively shown cross-sectionalside views of layers of particles 102 on which a fusing area 104 and anexample unfused thermal support area 106 have been formed. Withreference first to FIG. 10 , the unfused thermal support area 106 may beformed beneath the fusing area 104. That is, for instance, the fusingarea 104 may be formed directly on top of the particles 102 forming theunfused thermal support area 106. As shown in FIG. 1D, the unfusedthermal support area 106 may be formed above the fusing area 104 and asshown in FIG. 1E, a first unfused thermal support area 106 may be formedbeneath the fusing area 104 and a second unfused thermal support area106 may be formed above the fusing area 104. In addition or in otherexamples, unfused support areas 106 may be formed in variouscombinations of locations with respect to the fusing area 104. It shouldthus be understood that FIGS. 1A-1E may indicate that the unfusedthermal support area 106 may be formed on any side or on multiple sidesadjacent to the fusing area 104. As used herein, the term “adjacent”with reference to an unfused thermal area 106 may refer to any side,including laterally, below or above, the fusing area 104.

Turning now to FIG. 2 , there is shown a diagram of another example 3Dfabrication system 200 that may form an unfused thermal support area toreduce a rate at which particles forming a portion of a 3D objectthermally bleeds. The 3D fabrication system 200 may be similar to the 3Dfabrication system 100 depicted in FIG. 1A and may include many of thesame components. However, in the 3D fabrication system 200, the agentdelivery system 120 is depicted as including multiple delivery devices202, 204. That is, the agent delivery system 120 is depicted asincluding a first agent delivery device 202 that may deliver the fusingagent 122 and a second agent delivery device 204 that may deliver theenergy absorbing agent 124. As noted above, the energy absorbing agent124 may be the same as or may differ from the fusing agent 122.

Although not shown, the energy supply system 130 may also include asingle energy supply device or multiple energy supply devices. In anyregard, the energy supply system 130 may supply any of various types ofenergy. For instance, the energy supply system 130 may supply energy inthe form of light (visible, infrared, or both), in the form of heat, inthe form of electromagnetic energy, combinations thereof, or the like.According to examples, the type and/or amount of fusing agent 122 andenergy absorbing agent 124 deposited onto the particles 102 may be tunedto the type and strength of the energy that the energy supply system 130emits such that, for instance, the particles 102 may be heated asintended. By way of example, the tuning may be implemented to maximizethe heating of the particles 102 while minimizing the amount of energyapplied by the energy supply system 130.

The 3D fabrication system 200 may also include build platform 210, whichmay be in a build chamber within which 3D objects may be fabricated fromthe particles 102 provided in respective layers on the build platform210. Particularly, the build platform 210 may be provided in a buildchamber and may be moved downward as features of a 3D object are formedin successive layers of the particles 102. Although not shown, theparticles 102 may be supplied between a recoater 212 and the buildplatform 210 and the recoater 212 may be moved in a directionrepresented by the arrow 214 across the build platform 210 to spread theparticles 102 into a layer. In addition, the agent delivery system 120and the energy supply system 130 may be moved across the build platform210 as indicated by the arrow 216 to fuse together particles 102 inselected areas of layers of particles 102. For instance, the agentdelivery system 120 and the energy supply system 130 may be supported ona carriage that is to move in the directions 216. In some examples, therecoater 212 may be provided on the same carriage. In other examples,the agent delivery system 120 and the energy supply system 130 may besupported on separate carriages such that the agent delivery system 120and the energy supply system 130 may be moved separately with respect toeach other. In any regard, following formation of a layer of particles102 and a portion of a 3D object on the layer, the recoater 212 may beimplemented to form another layer and this process may be repeated tofabricate the 3D object.

Although not shown, the 3D fabrication system 200 may include a heaterto maintain an ambient temperature of the build envelope or chamber at arelatively high temperature. In addition or in other examples, the buildplatform 210 may be heated to heat the particles 102 to a relativelyhigh temperature. The relatively high temperature may be a temperaturenear the melting temperature of the particles 102 such that a relativelylow level of energy 132 may be applied to selectively fuse the particles102.

With reference now to FIG. 3 , there is shown a block diagram of anexample apparatus 300 that may cause an unfused thermal support area tobe formed adjacent to a selected area during formation of a portion of a3D object. It should be understood that the example apparatus 300depicted in FIG. 3 may include additional features and that some of thefeatures described herein may be removed and/or modified withoutdeparting from the scope of the apparatus 300. In addition, the featuresof the apparatus 300 are described with respect to the components of the3D fabrication systems 100, 200 discussed above with respect to FIGS. 1Aand 2 .

Generally speaking, the apparatus 300 may be a computing device, acontrol device of a 3D fabrication system 100, 200, or the like. Asshown in FIG. 3 , the apparatus 300 may include a controller 302 thatmay control operations of the apparatus 300. The controller 302 may beequivalent to the controller 110 discussed above. The controller 302 maybe a semiconductor-based microprocessor, a central processing unit(CPU), an application specific integrated circuit (ASIC), afield-programmable gate array (FPGA), and/or other suitable hardwaredevice.

The apparatus 300 may also include a memory 310 that may have storedthereon machine readable instructions 312-316 (which may also be termedcomputer readable instructions) that the controller 302 may execute. Thememory 310 may be an electronic, magnetic, optical, or other physicalstorage device that contains or stores executable instructions. Thememory 310 may be, for example, Random Access memory (RAM), anElectrically Erasable Programmable Read-Only Memory (EEPROM), a storagedevice, an optical disc, and the like. The memory 310, which may also bereferred to as a computer readable storage medium, may be anon-transitory machine-readable storage medium, where the term“non-transitory” does not encompass transitory propagating signals.

The controller 302 may fetch, decode, and execute the instructions 312to cause fusing agent 122 to be deposited onto a selected area, e.g., afusing area 104, of a layer of particles 102 of build material. Forinstance, the controller 302 may control the agent delivery system 120to deposit the fusing agent 122 onto the selected area of the layer ofparticles 102. The controller 302 may fetch, decode, and execute theinstructions 314 to cause an energy absorbing agent 124 to be depositedonto an unfused thermal support area 106 of the layer of particles 102that is adjacent to the selected area 104. For instance, the controller302 may control the agent delivery system 120 to deposit the energyabsorbing agent 124 onto the unfused thermal support area 106 of thelayer of particles 102. The controller 302 may fetch, decode, andexecute the instructions 316 to cause energy to be applied. Forinstance, the controller 302 may control the energy supply system 130 tosupply energy 132 onto the layer of particles 102, the deposited fusingagent 122, and the deposited energy absorbing agent 124. As discussedherein, application of the energy 132 may cause the particles 102 onwhich the fusing agent 122 has been deposited to be heated to atemperature above a melting point temperature of the particles 102 andthe particles 102 on which the energy absorbing agent 124 has beendeposited to be heated to a higher temperature that is below the meltingpoint temperature of the particles 102.

In other examples, instead of the memory 310, the apparatus 300 mayinclude hardware logic blocks that may perform functions similar to theinstructions 312-316. In yet other examples, the apparats 300 mayinclude a combination of instructions and hardware logic blocks toimplement or execute functions corresponding to the instructions312-316. In any of these examples, the controller 302 may implement thehardware logic blocks and/or execute the instructions 312-316.

Various manners in which the controller 110, 302 may operate arediscussed in greater detail with respect to the method 400 depicted inFIG. 4 . Particularly, FIG. 4 depicts a flow diagram of an examplemethod 400 for forming an unfused thermal support area 106. It should beunderstood that the method 400 depicted in FIG. 4 may include additionaloperations and that some of the operations described therein may beremoved and/or modified without departing from scope of the method 400.The description of the method 400 is made with reference to the featuresdepicted in FIGS. 1A-3 for purposes of illustration.

At block 402, the controller 110, 302 may control an agent deliverysystem 120 to deposit a fusing agent 122 onto a fusing area 104 of alayer of particles 102 of build material corresponding to an objectbeing fabricated.

At block 404, the controller 110, 302 may control the agent deliverysystem 120 to deposit an energy absorbing agent 124 onto an unfusedthermal support area 106 of the layer of particles 102.

At block 406, the controller 110, 302 may control an energy supplysystem 130 to supply energy 132 onto the layer of particles 102,including the deposited fusing agent 122 and the deposited energyabsorbing agent 124. As discussed herein, application of the energy 134may cause the particles 102 on which the fusing agent 122 has beendeposited to be heated to a temperature above a melting pointtemperature of the particles 102 and the particles 102 on which theenergy absorbing agent 124 has been deposited to be heated to a highertemperature that is below the melting point temperature of the particles102. As also discussed herein, by increasing the temperature of theparticles 102 in an area adjacent to the fusing area 104, the rate atwhich thermal bleed occurs among the particles 102 in the fusing area104 may be reduced. This may also result in the particles 102 in thefusing area 104 reaching and remaining at a temperature above a meltingpoint temperature of the particles 102 to cause the particles 102 tomelt and properly fuse together.

According to examples, at block 404, the controller 110, 302 may controlthe agent delivery system 120 to deposit the energy absorbing agent 124at a sufficiently low contone level to cause the particles 102 on whichthe energy absorbing agent 124 is deposited to remain unfused responsiveto receipt of energy from the energy supply system 130. In addition orin other examples, the controller 110, 302 may control the agentdelivery system 120 to deposit a mixture of the energy absorbing agent124 and a cooling agent and/or a defusing agent to cause the particles102 on which the energy absorbing agent 124 is deposited to remainunfused responsive to receipt of energy from the energy supply system130.

In other examples, the controller 110, 302 may determine whether thefusing area 104 corresponds to a portion of the object to be fabricatedthat has a size below a predefined size. In these examples, thecontroller 110, 302 may control the agent delivery system 120 to depositthe energy absorbing agent 124 in the unfused thermal support area 106based on the size of the fusing area 104 falling below the predefinedsize. In addition, the controller 110, 302 may not control the agentdelivery system 120 to deposit the energy absorbing agent 124 in anunfused thermal support area 106 based on the size of the fusing area104 meeting or exceeding the predefined size. In other words, thecontroller 110, 302 may control the agent delivery system 120 to form anunfused thermal support area 106 based on a determination that theparticles 102 in the fusing area 104 may not reach the melting pointtemperature without the unfused thermal support area 106.

Some or all of the operations set forth in the method 400 may beincluded as utilities, programs, or subprograms, in any desired computeraccessible medium. In addition, the method 400 may be embodied bycomputer programs, which may exist in a variety of forms both active andinactive. For example, they may exist as machine readable instructions,including source code, object code, executable code or other formats.Any of the above may be embodied on a non-transitory computer readablestorage medium.

Examples of non-transitory computer readable storage media includecomputer system RAM, ROM, EPROM, EEPROM, and magnetic or optical disksor tapes. It is therefore to be understood that any electronic devicecapable of executing the above-described functions may perform thosefunctions enumerated above.

Although described specifically throughout the entirety of the instantdisclosure, representative examples of the present disclosure haveutility over a wide range of applications, and the above discussion isnot intended and should not be construed to be limiting, but is offeredas an illustrative discussion of aspects of the disclosure.

What has been described and illustrated herein is an example of thedisclosure along with some of its variations. The terms, descriptionsand figures used herein are set forth by way of illustration only andare not meant as limitations. Many variations are possible within thespirit and scope of the disclosure, which is intended to be defined bythe following claims—and their equivalents—in which all terms are meantin their broadest reasonable sense unless otherwise indicated.

What is claimed is:
 1. A three-dimensional (3D) fabrication systemcomprising: a fusing agent; an energy absorbing agent different from thefusing agent, wherein the energy absorbing agent is a degradable agentthat is to evaporate or disintegrate within a predetermined time periodfollowing receipt of energy; an agent delivery system to deposit thefusing agent and the energy absorbing agent; an energy supply system;and a controller to: form a first feature by controlling the agentdelivery system to deposit the fusing agent onto a fusing area of alayer of particles of build material; determine a predefined size basedon a type of the particles, a type of the fusing agent, and a type ofenergy to be emitted by the energy supply system; determine that a sizeof the fusing area that forms the first feature is smaller than thepredefined size; based on the determination that the size of the fusingarea that forms the first feature is smaller than the predefined size,determine that a thermal support for the first feature is to befabricated; form the thermal support by controlling the agent deliverysystem to deposit the energy absorbing agent onto an unfused area of thelayer of particles, the unfused area being located adjacent to thefusing area; and control the energy supply system to supply the energyto the fusing area that forms the first feature and the unfused areathat forms the thermal support, wherein the supplied energy causes theparticles on which the fusing agent has been deposited to melt and atemperature of the particles in the unfused area to be raised to a levelthat is below a melting point temperature of the particles.
 2. The 3Dfabrication system of claim 1, wherein the controller is further tocontrol the agent delivery system to deposit droplets of the energyabsorbing agent to cause the particles in the unfused area to remainunfused responsive to receipt of the supplied energy.
 3. The 3Dfabrication system of claim 1, wherein the controller is further to:form a second feature by controlling the agent delivery system todeposit the fusing agent onto a second area of the layer of particles,the second area having a size larger than the predefined size; andcontrol the agent delivery system to not deposit the energy absorbingagent to areas adjacent to the second area in response to the secondarea having the size larger than the predefined size.
 4. The 3Dfabrication system of claim 1, wherein the agent delivery systemcomprises a first agent delivery device to deliver the fusing agent anda second agent delivery device to deliver the energy absorbing agent. 5.An apparatus comprising: a fusing agent; an energy absorbing agentdifferent from the fusing agent, wherein the energy absorbing agent is adegradable agent that is to evaporate or disintegrate within apredetermined time period following receipt of energy; an agent deliverysystem to deposit the fusing agent and the energy absorbing agent; anenergy supply system; a controller; and a memory storing machinereadable instructions that when executed by the controller cause thecontroller to: form a first feature by causing the agent delivery systemto deposit the fusing agent onto a selected area of a layer of particlesof build material; determine a predefined size based on a type of theparticles, a type of the fusing agent, and a type of energy to beemitted by the energy supply system; determine that a size of theselected area that forms the first feature is smaller than thepredefined size; based on the determination that the size of theselected area that forms the first feature is smaller than thepredefined size, determine that a thermal support for the first featureis to be fabricated: form the thermal support by causing the agentdelivery system to deposit the energy absorbing agent onto an unfusedarea of the layer of particles adjacent to the selected area; and causethe energy supply system to supply the energy to the selected area thatforms the first feature and the unfused area that forms the thermalsupport, wherein the supplied energy causes the particles in theselected area to be heated to a temperature above a melting pointtemperature of the particles and the particles in the unfused area to beheated to a temperature that is below the melting point temperature ofthe particles.
 6. The apparatus of claim 5, wherein the machine readableinstructions are further executable to cause the controller to causedroplets of the energy absorbing agent to be deposited at a sufficientlylow contone level to cause the particles on which the energy absorbingagent has been deposited to remain unfused responsive to the suppliedenergy.